高硅铝合金“Si-液膜-Si”单元力学特性及晶间液膜热裂机理研究

高硅铝合金（≥27wt.%）具有较高的热导率、可调节的膨胀系数、低密度及良好的机加工性，正成为国内外新一代空间电子器件封装材料。然而，高硅铝合金在激光封焊时易产生热裂，这与其凝固后期存在的“Si-液膜-Si”晶间液膜组织有关。有关晶间液膜热裂机制至今仍有一些问题没有弄清，现有的晶间液膜热裂模型，其理论结果和实验结果不完全相符。热裂的实验研究试样目前也均为多晶试样，其力学性能反映的是宏观整体的力学性能。目前还无法开展单个晶间液膜单元的力学实验研究，也无法弄清热裂是起源于液膜还是晶粒/液膜界面。本申请项目根据高硅铝合金凝固特点，构建“Si-液膜-Si”单个晶间液膜单元的力学研究系统，结合准固相区液相流变特性的研究，研究高硅铝合金晶间液膜单元的应力-应变本构方程和热裂组织特征，构建理论和实验结果相一致的晶间液膜热裂理论模型，研究晶间液膜热裂的机理，为防止焊件和铸件热裂提供理论指导。

With high thermal conductivity, adjustable expansion coefficient, low density and good machinability, hypereutectic high-silicon aluminum alloy (≥27wt.%) becomes a new packaging material for aerospace electronic devices home and abroad. However, hypereutectic high-silicon aluminum alloy is prone to hot tearing during laser welding, which can be attributed to the formation of intergranular liquid film of “Si-liquid film-Si” at the end of solidification. There are still problems in our understanding of the hot tearing mechanism of intergranular liquid film. In current hot tearing model of intergranular liquid film, theoretical results do not match exactly with experimental results. Current hot tearing experiments use polycrystal samples and the overall mechanical properties only on the macroscopic scale. Up till now, mechanical experimental research cannot be performed on a single intergranular liquid film unit, and whether hot tearing originates form the liquid film or from the grain/liquid film interface cannot be identified. This project constructs a mechanical research system of “Si-liquid film-Si” single intergranular liquid film unit in accordance with the solidification characteristics of hypereutectic high-silicon aluminum alloy. Combining this mechanical research system and the research of rheological properties of liquid alloys in quasi-solid zone, we will study the stress-strain constitutive equation and hot tearing microstructure characteristics of intergranular liquid film unit of high-silicon aluminum alloy, construct the theoretical model of hot tearing of intergranular liquid film with consistent theoretical and experimental results, study the mechanism of intergranular liquid film hot tearing, and provide theoretical reference for preventing hot tearing in welds and castings.